A number of systems have been employed to control the material flow from alternating piston pumps while pumping semiliquid or plasticized material containing aggregate chips, waste solids, concrete, etc., and channeling the discharge from the two pump cylinders into one discharge line. Generally this has been accomplished by employing a swiveling discharge pipe so that the inlet of the delivery pipe is connected to the outlet end of the discharge pipe during the appropriate phase on one of the pump cylinders. In other words, a connecting pipe is communicated alternately with the pump during the drive stroke of the pump for delivering the material from the pump to the discharge valves.
In arriving at an apparatus for accomplishing this oscillating movement of the connecting pipe, a number of problems have been incurred that have been characteristic of the apparatus used thus far. Often the apparatus is rather large and cumbersome requiring relatively substantial space for its operation. In addition, a thrust load imposed on the duct work during the power stroke of the piston has not been adequately compensated. Where compensation has been made to counteract these thrust forces additional structure exterior to the pipe apparatus has been required, adding to the need for even more space for the apparatus to operate properly. Due to the change in direction required by the connecting duct moment or torque forces are also created which produce undue wear on various parts of the apparatus if not compensated properly. The above has been a summary of some of the problems which have characterized apparatus and oscillating duct type pivotal discharge valves employed heretofore. Many of these problems as well as others have been overcome by the invention described herein.
The pivotal discharge apparatus of the invention described herein provides an economic and effective system to pump and channel discharge materials from two pump cylinders into the one line, substantially reducing, and in some cases eliminating, the problems noted above. The pivotal discharge valve of the invention employs a center pivot and thrust tube having a thrust plate extending radially therefrom supported for pivotal movement within a stationary housing. A pivotal arm attached to the pivot and thrust tube is actuated to oscillate a distribution duct between the two pump cylinders. Since the distribution duct makes about 180.degree. bend between the discharge pipe and the material pump, forces are imparted to certain parts of the apparatus. The thrust plate on the center of the pivot and thrust tube controls these forces in a plane perpendicular to the center axis of the pivot tube and relieves pivot support bushings of sustaining the full load of this plane. In addition, counterforce rollers may be placed at the top of the pivotal arm to counteract extreme forces experienced at the bottom of the pivotal arm during the power stroke in the material pump cylinders. Other apparatus such as wear plates, adjustment mechanisms, actuating mechanisms, etc., are discussed in detail in preferred embodiment which follows hereinafter. These features as well as more detailed features which will be discussed later herein overcome the problems which have been noted above and provide a compact, efficient apparatus for controlling the discharge in a multiple pump system.